1. Field of the Invention
This invention relates to enclosures for electronic equipment, and in particular to a stand alone dust and debris free enclosures for laser printers and the like, with means for air conditioning.
2. Prior Art
Electronic devices, by their very nature, contain components and parts that operate at varying degrees of electrical potential under normal operation. Dust and particulate matter which reside in the air become electrostatically charged and by electrostatic attraction can be drawn into the cabinet of an electronic device where they adhere to an oppositely charged component or part. Certain forms of electronic equipment such as photocopiers and laser printers include charged drums, which aggravate problems with electrostatic attraction. Other devices such as CRTs have components at very high potential. Whether or not the device uses electrostatic charge in operation, accumulation of dust and dirt greatly affects device performance and often its useful life. Of course, the dirtier the ambient air, and/or the higher the potential which exists on the electronic components and parts, the higher the rate of accumulation of the damaging, performance affecting matter. Furthermore, moisture may be absorbed in the accumulated dust.
Simply encasing the electronic device within a dust-tight cabinet is not a sufficient remedy. Electric and electronic devices dissipate heat. Enclosing a device in a dust-excluding enclosure reduces air exchange and traps the heat. While one could improve dust isolation, accumulation of heat would be greater. Conversely, opening pathways for air transfer allows ingress of dust. A fully air-tight enclosure as necessary for very good dust isolation traps most of the heat dissipated by an electronic device and may allow it to build to excessive levels. Heat can adversely affect electronic and mechanical components, or at least affect the operation of thermally sensitive components such as semi-conductors which are also affected adversely by excessively cold temperatures. It would be appropriate, therefore, to provide some sort of ventilating or air conditioning means not inconsistent with the general object of providing a dust free enclosure. In addition, such an enclosures should allow access to the equipment therein, particularly where the equipment includes a printer or photocopier that requires the user to load and remove sheets.
Prior art structures for protecting and/or cooling electronic devices include, for example, U.S. Pat. No. 4,493,267-Jedziniak. Jedziniak discloses a shelfing system for use with a data processing device, such as a personal computer. The disclosure provides means for affixing a terminal and a keyboard to the shelf system, thereby preventing unauthorized removal. Cooling blowers in the shelf surface are further provided. Blowers which merely increase airflow through a device can be counterproductive as they are powered means to draw dust into an enclosure. An effective means for completely enclosing a data processing device for clean and cool operation is not disclosed.
Computers and the like are characterized by a large number of densely mounted electronic components, including temperature sensitive semiconductors. Hastings, U.S. Pat. No. 4,589,712 discloses a cylindrical enclosure for housing electronic data processing equipment. Within the enclosure is a rack system with interconnected hollow support members which carry and emit blown cooled air. The rack itself is mounted on a turntable within the enclosure for rotating the equipment, reducing stagnation and heating of the ambient air. This device solves some of the problems associated with blowing air into an electronic device, but does not permit ready access to the contained electronic device.
U.S. Pat. No. 4,626,048 to Goodlander discloses a printer housing. The housing is a complete enclosure which is designed to be incorporated into a partitioning wall. The enclosure is openable from either side by way of hinged door panels, the printer being on a slidable shelf for easy access thereto. The enclosure is lined with sound deadening material and has means for drawing in air. Therefore, to some extent, the ventilating apparatus will also tend to collect dust. Since the device is designed to be incorporated into a wall, it is not readily movable.
U.S. Pat. No. 4,728,160 discloses a cabinet for an entire computer system. The cabinet has separate enclosures for each of the computer sub-systems. The cabinet includes cooling means for maintaining suitable ambient temperatures of the enclosed computer system. The device is an example of a large unit wherein the cooling and isolation from dust are addressed in the design of the unit as a whole. Where a user wishes to protect and manipulate the operating temperature of a prepackaged electronic device such as a printer, photocopier, etc., the user cannot practically redesign the unit for use on a particular premises where heat or dust may be a problem. The Mondor and Hastings references also disclose enclosures for housing self contained computer systems. There is no need to allow quick and repeat access to the contained devices.
It is necessary to have free and frequent access to a contained device when that device is, for example, a printer. Paper cassettes must be replaced, copies removed and often times paper jams must be cleared. Photocopiers further require access for loading originals. The prior art structures of Mondor and Hastings do not allow the necessary access to such enclosed devices.
Goodlander discloses a computer printer housing, having doors for easy accessibility. However, the device of Goodlander is a permanent structure made to be incorporated into a partitioning wall. Furthermore, the primary objective is the provision of sound-deadening means. Dust and dirt impermeability is not considered or disclosed, probably due to the relatively clean office environment where computer printers and the like are generally installed.
There is a need to provide an enclosure for electronic equipment which is movable and allows easy and ready access to the housed equipment. The enclosure must provide free access, adequate conditioning ventilation, and an impermeable barrier to dust and debris. Whereas these requirements are to some extent inherently conflicting, there is a need to optimally resolve them in a way that is applicable to generally available small scale printers, photocopiers and similar equipment. The enclosure could house items such as, for instance, laser printers in relatively dirty and dusty environs. Laser printers develop quite high voltages and are therefore extremely susceptible to air borne dust and dirt particles. The enclosure as herein provided has self-contained means for conditioning the air such as an on board air conditioning unit, a heat pump or perhaps a forced air fan and filter combination, in a portable carriage, for instance mounted on caster wheels, with substantially complete isolation from dust together with means to access the printer for service and operation.